Not Applicable
Not Applicable
1. Field of the Invention
In common use in the extrusion industry are water troughs for cooling and setting tubing and rods of various profiles as they flow from an extrusion die. Typically two vertical channels arranged opposite each other are located at one end of each water trough, and are utilized to retain a brass weir plate. The weir plate is constructed with an opening of a shape and size that closely approximates the desired profile of the tubing or rod. Therefore, the material being extruded flows from an extrusion die, through an opening in a weir plate, and into a water trough, where the extruded material is cooled and set in its final form. A thin film of water flows between the weir plate opening and the extruded material, preventing the extruded material from adhering to the weir plate. This water is then commonly channeled back inside the water trough by utilizing hoses or other means.
The present invention relates to the adjustability of the weir opening""s placement in relation to the weir plate. This is important because the water trough is typically moved away from the extruder each time the extruder is turned on, and it is often time-consuming to achieve perfect alignment between the water trough and extruder die each time. Proper alignment is necessary because the placement of the weir plate opening in relationship to the extruder die is crucial in achieving the desired profile. The distance between the weir plate opening and extruder die is important when extruding products that require precise internal dimensions.
The present invention also relates to the retention of the weir plate within a water trough, to the changeover from one extrusion profile to another, and to improved vision of the extruded material as it flows from the extrusion die and into the water trough.
2. Discussion of the Prior Art
As is shown in FIG. 1, commonly a weir plate is made of a lower portion 1 and an upper portion 2, each with half of the opening 3 that matches the desired profile. Often the opening is constructed with a counter-sunk proximal end to help guide the polymer into the opening. A new weir plate must be constructed for each new desired profile size or shape. The weir plate is commonly constructed of brass.
If the placement of the opening needs to be adjusted in relation to the extruder, the entire water trough must be moved to compensate. Moving the water trough in most cases is very awkward, and many times the stream of liquid polymer flowing through the weir plate is disrupted during the process and starts puddling on the floor. In addition, adjusting the height of one end of the water trough will change the water level, and the resulting change in depth of the tubing below the water surface will alter the water pressure and affect the shape of the tubing.
The present invention provides for a weir plate in which the size and shape of the weir opening can be easily changed. In one embodiment this is accomplished by utilizing a replaceable sizing insert, machined with desired size and shape opening. In another embodiment, the sizing insert comprises an adjustable mechanical iris, constructed with a lever with which the exact size of the weir opening can be adjusted.
Also provided is a weir plate in which the placement of the opening is easily adjustable. This is accomplished by utilizing at least one positioning stage, with one side fastened to the weir plate, and the other side fastened to a sizing insert holder. The weir plate is constructed with an oversized hole that is covered by a sealing plate. Therefore, movement of the weir opening can be accomplished by simply adjusting the positioning stage the appropriate distance, up or down, left or right, closer to the extruder or farther from the extruder.
Ball spring plungers are provided to tightly retain the weir plate within the vertical channels located in the typical water trough. Alternatively, a threaded tenor can be retained within a threaded portion of the weir plate and can be turned until it extends out of the weir plate the distance required to create a snug fit within the end of the water trough.
A tapered center-finder is provided that is used to rough-align the weir opening with the extruder die. The center-finder is simply placed inside the sealing plate assembly, and the weir opening is adjusted up or down, left or right, until the tapered end of the center-finder fits into the extrusion die center. After this, the extruder operator proceeds to place the sizing insert in the sealing plate assembly, and adjusts the positioning stage as needed after extrusion begins. The non-tapered end of the center-finder is used as a tool to help separate the sizing insert from the sizing insert holder when a different sizing insert is desired.
Stainless steel, polytetrafluoroethylene, or other heat and corrosion resistant materials are used because of the proximity to water and extreme heat. Polytetrafluoroethylene has the additional advantage of having nonstick properties.
The weir plate is preferably constructed of polycarbonate or other transparent material to improve visibility during set-up.
One of the advantages obtained with the present invention is providing for quick start-up each day, and quick changeover time between different profiles, which reduces manufacturing costs, and ultimately results in a lower retail price for the end product.